Rotary piston engine

ABSTRACT

A rotary piston engine wherein an auxiliary mixture chamber into which fuel is injected from a nozzle is provided between a suction port and an ignition plug in a center housing. A mixture injection member which reciprocatingly slides in accordance with the rotation of a rotor is provided in the auxiliary mixture chamber, and a communicating hole of the auxiliary mixture chamber communicates with each of the working chambers of the rotary piston as each chamber moves past the hole. As each working chamber goes through its suction stroke, a portion of the lean air/fuel mixture sucked in from the carburetor is also sucked into the auxiliary mixing chamber for mixture with fuel from the nozzle to produce a rich air/fuel mixture which is subsequently ejected into the lean air/fuel mixture in the working chamber. The lean and rich mixtures of air/fuel are then compressed in the working cylinder and ignited by the ignition plug.

United States Patent [1 1 Arai [ ROTARY PisToN ENGINE [75] Inventor: Fuminao Arai, Kariya, Japan [73] Assignee: Aisin Seiki Kabushiki Kaisha,

' Kariya, Japan [22] Filed: Feb. 20, 1974 [21] Appl.'No.: 443,995

[30] Foreign Application Priority Data Feb. 23, 1973 Japan 48-22451 [52] US. Cl. l23/8.l3 [51] Int. Cl. F02B 53/04 [58] Field of Search... 123/809, 8.11, 8.13, 33 VC, 123/33 C, 32 ST [56] References Cited UNITED STATES PATENTS 3,805,747 4/1974 Nakagawa et al. l23/8.13

FOREIGN PATENTS OR APPLICATIONS 1,144,053 2/1963 Germany 123/809 [451 Sept. 23, 1975 Primary ExaminerC. J. Husar Assistant Examiner-Michael lKoczo, Jr.

Attorney, Agent, or FirmStevens, Davis, Miller & Mosher [57] ABSTRACT A rotary piston engine wherein an auxiliary mixture chamber into which fuel is injected from a nozzle is provided between a suction port and an ignition plug in a center housing. A mixture injection member which reciprocatingly slides in accordance with the rotation of a rotor is provided in the auxiliary mixture chamber, and a communicating hole of the auxiliary mixture chamber communicates with each of the working chambers of the rotary piston as each chamber moves past the hole. As each working chamber goes through its suction stroke. a portion of the lean air/fuel mixture sucked in from the carburetor is also sucked into the auxiliary mixing chamber for mixture with fuel from the nozzle to produce a rich air/fuel mixture which is subsequently ejected into the lean air/fuel mixture in the working chamber. The lean and rich mixtures of air/fuel are then compressed in the working cylinder and ignited by the ignition plug.

2 Claims, 4 Drawing Figures 1 ROTARY PISTON ENGINE BACKGROUND OF THE INVENTION The present invention relates to a rotary piston engine, and more particularly to a rotary pistonjengine of the trochoid structure.

As compared with a reciprocating engine, a rotary piston engine is large in the ratio between the surface area of combustion chamber S and the volume of the combustion chamber V, that is S/V. For this reason, the cooling effect of the surface of the combustion chamber is great, and the combustion temperature is low. The rotary piston engine consequently has the advantage of little NO, exhaust.

In the rotary piston engine, however, the combustion temperature is low, and the quenching zone, in which the mixture is incombustible due to the cooling, is in the vicinity of the surface of the combustion chamber. Therefore fuel particles supplied into the cylinder which have not perfectly vaporized are incompletely combusted and adhere to the cylinder surface, and are exhausted in such condition. As a result, the quantities of exhaust of unburnt HC and CO attributed to the incomplete combustion are large, which is a cause of air pollution. Also such poor combustion results in large and excessive fuel consumption.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the deficiency of the rotary piston engine that the exhaust of HC and CO is of large amount, without spoiling the advantage of same that the exhaust of N0 is of small amount.

A further object of the present invention is to reduce the fuel consumption of the rotary piston engine.

In order to accomplish these objects, according to the present invention, a lean air/fuel mixture portion is formed on the cylinder surface side within the cylinder of a rotary piston engine, while a rich air/fuel mixture portion is formed at the central part of the cylinder or around an ignition plug, to effect the so-called stratified mixture supply, whereby the exhaust of NO is reduced and an incomplete combustion portion within the cylinder is also prevented without raising the combustion temperature.

BRIEF DESCRIPTION'OF THE DRAWIN In the accompanying drawing:

FIG. 1 shows a cross section of the central part of a rotary piston engine according to the present invention;

FIGS. 2 and 3 show cross sections of a part of FIG. 1 in different operating positions; and

FIG. 4 shows a cross section of a modification of the part in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS which it is held within the cylinder 13. At the central part of a piston 12, there is provided a bearing surface 12a on which the eccentric portion 27a of the output shaft 27 is fittedly supported. The piston 12 is shaped into a substantially triangular plate whose outer pierphery is formed into the inner envelope of the peritrochoid, and is rotatably fitted into the cylinder 13. Piston 12 is rotated in such manner that seal members 31a, 3 lb and 31c respectively fitted into grooves at the three corners of the substantially triangular plate are incessantly held in airtight contact with the inner pe ripheral surface of the center housing 11.

In both side surfaces of the piston 12, grooves (not shown) are provided in which seal members (not shown) are placed for keeping airtightness between both the side surfaces and both the side plates.

The cylinder 13 is partitioned into three working chambers 13a, l3b and 13c by the center housing 11, both the side plates, and the piston 12. Upon rotation of the piston 12 about shaft 27, the working chambers 13a, 13b and move around the shaft 26 while changing in volume. Above and below the central part of the left-hand side of the center housing 11, that is, at parts communicating with the left lower part of the first working chamber 13a and with the left upper part of the third working chamber 130 when the piston 12 is in the position illustrated in FIG. 1, there are respectively formed a suction port 11a and an exhaust port 11b. On the upper side of the center housing 11, more specifically, past the suction port as viewed in the di rection of rotation (the direction of an arrow A) of the piston 12 in FIG. 1 and adjacent one end of the first working chamber 13a, there is provided a communication hole 18 which provides a passage between an auxiliary mixture chamber 16 of a cylindrical shape and the first working chamber 13a. A fuel injection nozzle 17 for injecting fuel into the auxiliary mixture chamber is provided at a suitable position of the side wall of the auxiliary mixture chamber 16. A mixture push'out member 19 is fittedly inserted into the auxiliary mixture chamber 16 in a manner to be hermitically sealed and slidable on the side wall thereof. Over the auxiliary mixture chamber 16 is a stopper 20 which limits upward movement of the mixture push-out member 19. The stopper 20 may be press-fitted or screwed into housing 11. Provided at the central part of the stopper 20 is a through hole 20b, through which a rod portion 19a of the mixture push-out member 19 penetrates. A spring retainer 23 is fastened at the upper end part of the rod portion 19a. Between the spring retainer and the stopper 20, there is extended a spring 21, which normally urges the mixture push-out member 19 upwards as viewed in the drawings. Above the rod portion 19a along its longitudinal axis, a cam 24 is disposed which is secured to and rotates about a shaft extending in a direction orthogonally intersecting the aforesaid axis of rod portion 19a. The cam 24 is driven by the output shaft 27 through a chain, gearing or the like, (not shown). The number of revolutions of cam 24 is made three times as large as that of the piston 12. Shown at 28 is a cover which covers the cam 24, the rod portion 19a, etc. An ignition plug 25 is disposed above the central part of the right-hand side of the center housing 11, that is, above the central part of the second working chamber 13b as viewed when the piston 12 is in the position illustrated in FIG. 1.

The operation based on the foregoing construction will now be explained.

It is well known that, in the rotary piston engine of the trochoid structure, the four strokes of suction compression explosion exhaust are carried out by varying the volume of the working chamber with the rotation of the piston.

The first working chamber 13a in FIG. 1 is in the course of the suction stroke, and is sucking in a lean air/fuel mixture from a carburetor (not shown) through the suction port 11a. The second working chamber 13b is close to the end of the compression stroke. The third working chamber 130 is under the exhaust stroke. The mixture to be sucked in through the suction port 11a is approximately 18 22 in air/fuel ratio, and is leaner than the mixture of the ideal air/fuel ratio 14.7. When the piston 12 is in the position of FIG. 1, the cam 24 is at a position at which the rod 19a of the mixture pushout member 19 can be shifted to the uppermost end by the force of the spring 21 in synchronism with the rotation of the piston 12. While the mixture push-out member 19 comes from the lowermost end or the position shown in FIG. 3 to the uppermost end or the position shown in FIG. 1, a portion of the lean air/fuel mixture which the first working chamber 13a has sucked in through the suction port 11a is sucked into the auxiliary mixture chamber 16 through the communication hole 18. In the stroke in which the mixture push-out member 19 moves towards the uppermost end, immediately after the underside of the mixture push-out member 19 passes an opening at the fore end of the fuel injection nozzle 17, fuel of an amount corresponding to a load is injected from the fuel injection nozzle 17 into the spiral vortices of the lean mixture generated within the auxiliary mixture chamber 16. Thus, a rich mixture having an air/fuel ratio of, for example, about 13 is produced within the auxiliary mixture chamber 16. Subsequently, when the piston 12 rotates to bring the various parts to approximately the position in FIG. 2 in which the communication between the first working chamber 130 and the suction port 11a is cut off, the first working chamber 13a terminates the suction stroke and transfers to the compression stroke. At this time, the cam 24 rotating in synchronism with the rotation of the piston 12 begins to press and shift the rod 19a of the mixture push-out member 19 downwards as viewed in the figure. Therefore, the mixture push-out member 19 begins to eject the rich mixture in the auxiliary mixture chamber 16 through the communicating hole 18 into the lean mixture of air/fuel in the first working chamber 13a.

At this time, since the piston 12 is continuing to rotate in the direction of the arrow A, the position of the various part shown in FIG. 2 is shifting to the positions of the various part shown in FIG. 3, and the lean mixture in the first working chamber 13a is also rotating in the direction of rotation of the piston 12. Since, however, the auxiliary mixture chamber 16 and the communication hole 18 are slanted in the direction of rotation of the piston 12, the rich mixture ejected from the auxiliary mixture chamber 16 into the first working chamber 13a enters at substantially the central part of the flow of the lean mixture and is mixed with the lean mixture.

From the point of ejection of the rich mixture, the piston 12 is further rotated in the direction of the arrow A, and the compression stroke is almost terminated,

the first working chamber 13a in FIG. 2 comes to the position of the second .working chamber in FIG. 1. At this time, as the working chamber rotates, the rich mixture of large specific gravity is moved outwardly by a centrifugal force, so that a mixture of good ignitability is produced in the vicinity of the ignition plug. As seen in the second working chamber 13b in FIG. 1, there arises a distribution of two layers of air/fuel mixture in which the outer peripheral portion or layer consists of the lean mixture and the rich mixture of suitable strength is included in a portion or layer at the central part and in the vicinity of the ignition plug.

When the first'working chamber 13a has come to the position of the second working chamber 13b shown in FIG. 1, the mixture of suitable strength at the central part is ignited by the ignition plugs 25a and 25b (it will be understood that only one ignition plug 25a may be provided), and the combustion begins. Subsequently, the lean mixture at the outer peripheral part burns. Owing to the expansion of the gas at this time, a turning force is bestowed on the piston 12 in the direction of the arrow. The turning force is transmitted to the output shaft 27 through the eccentric portion 27a, and is taken out as output. Upon further rotation of the piston 12, the first working chamber 13a rotates in the direction of the arrow A while increasing the area of working chamber. When the first working chamber 13a communicates with the exhaust port 1112, it decreases the area of working chamber while discharging the combustion gas through the exhaust port 11b. The engine at this point has terminated one complete cycle thereof. Thereafter, it comes to the position of the first working chamber 13a in FIG. 1 again, and the cycle which has thus far been explained is repeated.

The second working chamber 13b and the third working chamber 13c similarly operate with the respective phase shifts of l20 from the first working chamber. At the central part of the underside of the mixture push-out member '19, there is provided a projecting portion 19b which fits in the communicating hole 18 in a nearly hermetic state when the mixture push-out member 19 has shifted to the lowermost end as shown in FIG. 3. The projecting portion 19b diminishes the force by which the compression pressure of the compression stroke in the working chamber 13a, 13b, 13c

acts on the mixture push-out member 19 after the ejection of the rich mixture from the auxiliary mixture chamber 16. Shown at 20a is an air vent which communicates with the atmospheric air so that, when the mixture push-out member 19 is moved by the cam 24, the movement may not be hindered.

A modified embodiment of the portion of the auxiliary mixture chamber 16 as well as the mixture pushout valve 19 of the present invention will now be described with reference to FIG. 4. The same symbols in FIG. 4 as those in FIGS. 1-3 designate the same members or members effecting the same functions.

The points of difference of the embodiment in FIG. 4 from the embodiment in FIG. 1 are as stated below. The lower end part of the mixture push-out member 19 is provided with a'hem'ispherical surface, the lower end surface of the auxiliary mixture chamber 16 is also provided with a hemispherical surface coincident with the hemispherical surface of the member 19, and the communicating hole 18 is slanted and spaced from the center of the hemisphericalsurface of the chamber 16, so that upon suction, an intense spiral vortex is generated within the auxiliary mixture chamber 16, and upon injection of the fuel from the fuel injection nozzle 17, good mixing is conducted by the spiral vortex. A seal member 29 is interposed between the mixture push-out member 19 and the cylinder surface of the auxiliary mixture chamber 16. A rocker arm 27 which is pivotally supported by a shaft 26 is provided between the cam 24 and the rod portion 19a of the mixture push-out member 19.

As described above in detail, according to the present invention, an auxiliary mixture chamber is provided on the suction side of a center housing in a rotary piston engine which forms a layer of a rich mixture of suitable strength in the neighborhood of the central part of each working chamber and a layer of a lean mixture outside the rich mixture layer or at parts in contact with the center housing, side plates and piston, so that the stratified mixture supply is carried out to slowly and re liably burn the lean mixture by combustion of the lean mixture, thereby to prevent unburnt gas from being discharged and to prevent HC and CO from being discharged in large quantities. Besides, since the combustion speed can be made lower than in a prior art rotaty piston engine to which a uniform mixture having an air fuel ratio of about 14.7 is supplied, the combustion temperature can be lowered, and the exhaust concentration of NO can be made very low. Furthermore, since the wasteful exhaust of HC and CO is lessened, the fuel consumption is decreased.

What is claimed is:

1. In a rotary piston engine having a case which includes a center housing with a polyarcuate inner peripheral surface and side plate portions for hermetically sealing the side parts of said center housing, a polygonal piston being provided within said case in a manner to be eccentrically rotatable therein, said piston sliding along the inner peripheral surface of said center housing at corner end parts of said piston, the interior of said case being partitioned into a plurality of working chambers, the volume of said each working chamber being varied at the sliding of said piston within said case, a suction port and an exhaust port being providedin said case, the improvement comprising a cylindrical auxiliary mixture chamber at an outer peripheral part of said center housing, means defining a communication hole in said center housing for fluidly communicating said auxiliary mixture with the interior of the particular working chamber communicating with said suction port, a nozzle and a mixture push-out member within said auxiliary mixture chamber, said nozzle being adapted to inject fuel into said auxiliary mixture chamber, a shaft driven by said piston, said mixture push-out member sliding airtightly on a cylindrical inner peripheral surface of said auxiliary mixture chamber and reciprocatingly driven by said shaft driven by said piston to inject a mixture in said auxiliary mixture chamber into said particular working chamber, so that in an engine cycle suction stroke of sucking only a lean mixture of air/fuel through said suction port, after the particular corner end part of said piston within said particular working chamber as situated on the fore side in the direction of rotation passes said communication hole, said mixture push-out member is caused to suck a portion of said lean mixture of air/fuel from within said particular working chamber into said auxiliary mixture chamber and simultaneously to inject the fuel from said injection nozzle so as to produce a rich air/fuel mixture within said auxiliary mixture chamber, and that in a period of the cycle from the approximate termination of the suction stroke of said particular working cham her to the first half of a compression stroke, said mixture push-out member is caused to inject said rich mixture in said auxiliary mixture chamber into said particular working chamber through said communication hole.

2. In the rotary piston engine according to claim 1, further comprising: an ignition plug, the front end of said mixture push-out member is hemispherical, seal means between said mixture push-out member and said cylindrical surface of said auxiliary mixture chamber, said communication hole is made eccentric to said mixture push-out member, and the interior of said communication hole is inclined towards said ignition plug. 

1. In a rotary piston engine having a case which includes a center housing with a polyarcuate inner peripheral surface and side plate portions for hermetically sealing the side parts of said center housing, a polygonal piston being provided within said case in a manner to be eccentrically rotatable therein, said piston sliding along the inner peripheral surface of said center housing at corner end parts of said piston, the interior of said case being partitioned into a plurality of working chambers, the volume of said each working chamber being varied at the sliding of said piston within said case, a suction port and an exhaust port being provided in said case, the improvement comprising a cylindrical auxiliary mixture chamber at an outer peripheral part of said center housing, means defining a communication hole in said center housing for fluidly communicating said auxiliary mixture with the interior of the particular working chamber communicating with said suction port, a nozzle and a mixture push-out member within said auxiliary mixture chamber, said nozzle being adapted to inject fuel into said auxiliary mixture chamber, a shaft driven by said piston, said mixture push-out member sliding airtightly on a cylindrical inner peripheral surface of said auxiliary mixture chamber and reciprocatingly driven by said shaft driven by said piston to inject a mixture in said auxiliary mixture chamber into said particular working chamber, so that in an engine cycle suction stroke of sucking only a lean mixture of air/fuel through said suction port, after the particular corner end part of said piston within said particular working chamber as situated on the fore side in the direction of rotation passes said communication hole, said mixture push-out member is caused to suck a portion of said lean mixture of air/fuel from within said particular working chamber into said auxiliary mixture chamber and simultaneously to inject the fuel from said injection nozzle so as to produce a rich air/fuel mixture within said auxiliary mixture chamber, and that in a period of the cycle from the approximate termination of the suction stroke of said particular working chamber to the first half of a compression stroke, said mixture push-out member is caused to inject said rich mixture in said auxiliary mixture chamber into said particular working chamber through said communication hole.
 2. In the rotary piston engine according to claim 1, further comprising: an ignition plug, the front end of said mixture push-out member is hemispherical, seal means between said mixture push-out member and said cylindrical surface of said auxiliary mixture chamber, said communication hole is made eccentric to said mixture push-out member, and the interior of said communication hole is inclined towards said ignition plug. 